1. Field of the Invention
The present invention relates to an infrared-light-absorption gas concentration measurement device.
2. Description of the Related Art
A gas concentration measurement device that uses the non-dispersive infrared (NDIR) absorption method is an example of a known concentration measurement device for measuring the concentration of a specific component contained in sample gas or the like. This type of gas concentration measurement device causes sample gas to absorb infrared light emitted from a light source, and then detects the amount of infrared light that has passed through an optical filter (band pass filter) with a detector. The concentration of the sample gas is determined on the basis of the amount of light with a specific wavelength that has been absorbed.
Japanese Unexamined Patent Application Publication No. 5-203573, for example, discloses such a gas concentration measurement device. The gas concentration measurement device disclosed in Japanese Unexamined Patent Application Publication No. 5-203573 is capable of measuring a plurality of types of sample gas by rotating a disc on which a plurality of band pass filters are arranged with intervals therebetween in a circumferential direction.
However, in the gas concentration measurement device disclosed in Japanese Unexamined Patent Application Publication No. 5-203573, the band pass filter to be used is switched by rotating the disc around a rotation axis that is parallel or substantially parallel to the direction in which the band pass filter and the detector are arranged during the measurement. The disc is relatively large because the band pass filters are arranged in the circumferential direction on the disc. Accordingly, the gas concentration measurement device is required to have a rotation region in which the disc rotates, and is therefore also large. It is difficult to install such a large gas concentration measurement device in a relatively small space.